1. Field of the Invention
The present invention relates to a bonding apparatus and a bonding method performed with the bonding apparatus. The bonding apparatus involves apparatuses such as a bump bonding apparatus for forming projecting electrodes on semiconductor integrated circuits (referred to as ICs hereinafter) in fabricating flip chip type ICs, and a wire bonding apparatus for connecting the ICs with substrate electrodes via a gold wire, or the like.
2. Description of the Related Art
A stud bump bonding technique has been known, which is a technique for joining gold bumps to electrode formed points on flip chip ICs with ultrasound supplied by adopting a wire bonding technique of the ICs. The stud bump bonding technique will be described below.
A generally used conventional bump bonding apparatus is shown in FIG. 12, for example. In this bump bonding apparatus, a gold wire 1 is held by a clamper 2 and passed through a capillary 3. The capillary 3 is provided at a leading end part of an ultrasonic horn 4, which is disposed on a supporting frame 5 that is swingable via a horizontal axial center 5a. The supporting frame 5 is moved in a direction of an arrow 21 by ahead up-down driving device 6, whereby the capillary 3 is moved up and down via the ultrasonic horn 4. A voice coil motor is used as the head up-down driving device 6. The ultrasonic horn 4 has an ultrasonic oscillator 7.
The supporting frame 5 is provided on a moving table 8 that is movable in X-Y directions which are orthogonal to each other in a horizontal direction. Thus, the capillary 3 is moved in the horizontal direction through movement of the moving table 8. 9 is a detecting sensor for detecting a positional change in an up-down direction of the supporting frame 5. A position in an up-down direction of the capillary 3 is obtained on a basis of output information from the detecting sensor 9.
Above the clamper 2 is arranged an air tensioner 10 for drawing the gold wire 1 upwardly. On the other hand, a heat stage 12 is disposed under the capillary 3 for holding and heating an IC 11. A spark generating device 14 set in a vicinity of a leading end of the gold wire 1, which is inserted into the capillary 3, generates a spark between the device 14 and the leading end of the gold wire, thereby melting the gold wire 1 and forming a gold ball 16. A camera device 15 for recognizing a position of the IC 11 is installed above the heat stage 12.
The conventional bump bonding apparatus in the above constitution operates in a manner as described below.
First, a spark is applied from the spark generating device 14 to the leading end of the gold wire 1 that extends downwardly from the capillary 3, whereby the gold ball 16 is formed. The IC 11 on the heat stage 12 is recognized by the camera device 15 and then, based on information obtained the recognizing operation, the gold ball 16 is positioned by driving the moving table 8.
Next, the capillary 3 is moved downwardly by the head up-down driving device 6. Then, when the gold ball 16 comes into contact with an electrode formation point of the IC 11 from above the electrode formation point, an up-down shift of the supporting frame 5 detected by the detecting sensor 9 remains at a constant value, whereby a position of the electrode formation point of the IC 11 is detected. A predetermined force is impressed to the capillary 3 to press the gold ball 16 downwardly. Further, ultrasonic wave oscillation is applied via the ultrasonic horn 4 from the ultrasonic oscillator 7 to join the gold ball 16 to the electrode formation point of the IC 11. A bump is thus formed at the electrode formation point of the IC 11. Thereafter, the capillary 3 is moved upwardly a fixed distance by the head up-down driving device 6 and, the gold wire 1 is pulled up by the head up-down driving device 6 with the wire 1 being held by the damper 2. As a result, the gold wire 1 on the bump is cut at a recrystallization boundary zone in the gold wire produced by the spark, thereby forming a projecting bump 17 on the electrode formation point of the IC 11.
However, a pitch of electrodes on the IC becomes narrower and consequently a diameter at a base of the bump becomes 65 xcexcm or smaller. That is,the size of the bump is getting smaller. Thus, the following problems arise. Specifically, when the gold ball 16 comes into contact with the electrode formation point of the IC 11 from above of the electrode formation point, a total inertia of the damper 2, capillary 3, ultrasonic horn 4, ultrasonic oscillator 7, supporting frame 5, head up-down driving device 6, and shift detecting sensor 9 is applied as an impact force to the gold ball 16. Thus, as the bump becomes smaller in size, the impact force is large enough to crush the gold ball 16. Thereafter, by applying the ultrasonic wave oscilation to the bump, a problem in that a predetermined height of the bump cannot be obtained results.
On the other hand, in order to restrict the above impact force, if the speed of the capillary 3 is lowered when the gold ball 16 comes into contact with the electrode formation point of the IC 11, a problem in that production cycle time is disadvantageously lengthy results. Even in the case of normal bumps having a diameter of 65-90 xcexcm, the same problem results if the speed of the capillary 3 is increased, so as to shorten the production cycle time when the gold ball 16 comes into contact with the electrode formation point of the IC 11.
The present invention is accomplished in order to eliminate the above-described problems. An object of the present invention is therefore to provide a bonding apparatus which can shorten a bump formation time and form bumps stably, and also to provide a bonding method performed with the bonding apparatus.
In order to achieve the aforementioned objective, a bonding apparatus is provided according to a first aspect of the present invention, which comprises:
a reduced inertial moving and pressing device having a wire guide member for guiding a wire having a melt ball at a leading end thereof, and a driving part, for moving the wire guide member together with the melt ball from a location that corresponds to the position of melt ball immediately before the melt ball touches an electrode of a semiconductor integrated circuit, and for pressing and joining the melt ball to the electrode; and
a higher speed moving device for moving a move frame having the reduced inertial moving and pressing device;
wherein the reduced inertial moving and pressing device is moved together with the higher speed moving device at a higher speed to the location that corresponds to the position of the melt ball immediately before the melt ball touches the electrode, and is then moved from this location to the electrode at a speed lower than the higher speed, with an inertia caused by the higher speed movement of the reduced inertial moving and pressing device being reduced.
The reduced inertial moving and pressing device can further include an ultrasonic oscillation device set to the wire guide member for ultrasonically oscillating the melt ball via the wire guide member when the melt ball is pressed to the electrode.
The reduced inertial moving and pressing device may be set to the move frame so as to move relatively to the move frame for reducing the inertia of the reduced inertial moving and pressing device.
In an arrangement, the reduced inertial moving and pressing device may have the wire guide member disposed at one end part of the reduced inertial moving and pressing device, and the driving part disposed at another end part thereof. The reduced inertial moving and pressing device is set to the move frame with the wire guide member and the driving part being rocked via an oscillating shaft that is set to the move frame.
The ultrasonic oscillation device may be arranged separately from the move frame, while having a transmitting member for transmitting ultrasonic oscillation generated at the ultrasonic oscillation device to the wire guide member.
In the bonding apparatus, the move frame may have the reduced inertial moving and pressing device at one end part of the move frame and the higher speed moving device at another end part thereof The move frame is rocked via a frame oscillation shaft. The higher speed moving device has a cam mechanism set to the another end part for rocking the move frame, with the oscillating shaft of the reduced inertial moving and pressing device being arranged at a balanced position where the oscillating shaft balances with the frame oscillation shaft in terms of inertia.
According to a second aspect of the present invention, there is provided a bonding apparatus which comprises:
a moving device which moves a move frame having a wire guide member at a second speed to a location that corresponds to the position of a melt ball immediately before the melt ball, formed at a wire leading end projecting from the wire guide member, touches an electrode of a semiconductor integrated circuit, moves the move frame towards the electrode at a first speed lower than the second speed, and causes the wire guide member to press and join the melt ball to the electrode after the melt ball touches the electrode of the semiconductor integrated circuit;
an ultrasonic oscillation device set separately from the move frame for ultrasonically oscillating the melt ball when the melt ball is being pressed to the electrode; and
a transmitting member for transmitting the ultrasonic oscillation generated by the ultrasonic oscillation device to the wire guide member so as to ultrasonically oscillate the melt ball.
According to a third aspect of the present invention, there is provided a bonding method comprising:
moving a melt ball at a second speed towards an electrode of a semiconductor integrated circuit until the melt ball reaches a locationn that corresponds to a position of the melt ball immediately before the melt ball touches the electrode; and
after the melt ball reaches this location, moving, pressing and joining the melt ball to the electrode at a first speed lower than the second speed with a lower inertia produced by reducing a higher inertia resulting from the movement at the second speed.
According to the bump bonding apparatus in the first aspect of the present invention as is fully described hereinabove, the higher speed moving device, and the reduced inertial moving and pressing device are set. The operation of moving the wire guide member at high speed with the higher speed moving device, and the operation of pressing and moving the wire guide member with low inertia are performed, independently and separately of each other. Thus, since the inertia at the reduced inertial moving and pressing device is reduced, the impact force, when the formed melt ball projecting from the wire guide, member is driven by the reduced inertial moving and pressing device and comes into contact with the electrode of the semiconductor integrated circuit, is restricted. Accordingly, minute bumps can be stably formed, and can be prevented from being defective in shape while improved in quality. Meanwhile, the operation other than pressing and joining the melt ball to the electrode is carried out by driving the wire guide member by the higher speed moving device, so that productivity is improved without increasing production cycle time.
The reduced inertial moving and pressing device is provided with the ultrasonic oscillation device. The ultrasonic oscillation device applies ultrasonic oscillation to the melt ball when the melt ball is being pressed to the electrode. The melt ball can accordingly be joined to the electrode more easily and firmly.
Since the reduced inertial moving and pressing device swings via the oscillating shaft which is set at the balanced position to balance with the frame oscillation shaft of the move frame in terms of inertia, effects of the wire guide member onto the reduced inertial moving and pressing device are eliminated, thereby further contributing to the above-mentioned stable formation of minute bumps and productivity improvement.
When the ultrasonic oscillation device is set separately from the move frame, the inertia of the reduced inertial moving and pressing device is reduced even more, thereby contributing to the stable formation of minute bumps and improvement in productivity.
According to the bump bonding apparatus in the second aspect of the present invention, the moving device for the wire guide member and the ultrasonic oscillation device are eliminated from the move frame, so that the inertia of the move frame is reduced. The high speed movement of the melt ball, and the pressing and movement of the melt ball with low inertia can be performed by one moving device. Further, the stable formation of minute bumps and productivity improvement can be realized.